Method of manufacturing circuit board

ABSTRACT

A method for manufacturing a circuit board comprises steps of providing a single-sided board comprising a first insulating base, a copper layer, and at least one first conductive structure; providing a laminated board comprising a metal layer, a third insulating base, a metal shielding layer, and a second insulating base; forming a wiring layer by the metal layer comprising at least one signal wire and at least one connecting pad; defining at least one second through hole each passing through the second insulating base, the metal shielding layer, and the third insulating base; forming a second conductive structure in each second through hole; providing a double-sided board comprising a wiring layer, a fourth insulating base, a first copper foil; and at least one third conductive structure; pressing the single-sided board, at least one middle structure, and the double-sided board in that sequence to form the circuit board.

FIELD

The subject matter herein generally relates to a circuit board,especially relates to a method of manufacturing a circuit board.

BACKGROUND

Signals transmitted by the signal wires of the circuit board aresusceptible to electromagnetic interference. At present, at least oneshielding layer is pressed on the wiring layer and connects the wiringlayer to protect signals transmitted from electromagnetic interference.However, the above-described method requires processes with highaccuracy

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present disclosure will now be described, by wayof embodiments only, with reference to the attached figures.

FIG. 1 is a flowchart of a first embodiment of a method formanufacturing a circuit board.

FIGS. 2-8 are cross-sectional views of illustrating respective steps ofa first embodiment of a method for manufacturing the circuit board.

FIG. 9 is a flowchart of an embodiment of a method for manufacturing asingle-sided board.

FIGS. 10-11 are cross-sectional views of illustrating respective stepsof a method for manufacturing the single-sided board.

FIG. 12 is a flowchart of an embodiment of a method for manufacturing alaminated board.

FIGS. 13-14 are cross-sectional views of illustrating respective stepsof a method for manufacturing the laminated board.

FIG. 15 is a flowchart of an embodiment of a method for manufacturing adouble-sided board.

FIGS. 16-17 are cross-sectional views of illustrating respective stepsof a method for manufacturing the double-sided board.

FIG. 18 is a cross-sectional view of an insulating removable layerapplied to form a middle structure of FIG. 6 .

FIG. 19 is a flowchart of a second embodiment of a method formanufacturing a circuit board.

FIGS. 20-24 are cross-sectional views of illustrating respective stepsof a second embodiment of a method for manufacturing the circuit board.

FIG. 25 is a cross-sectional view of another embodiment of a method formanufacturing the circuit board.

FIG. 26 is a cross-sectional view of an embodiment of a circuit board.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale, and the proportions of certain parts maybe exaggerated to better illustrate details and features of the presentdisclosure.

The term “comprising,” when utilized, means “including, but notnecessarily limited to”; it specifically indicates open-ended inclusionor membership in the so-described combination, group, series, and thelike.

FIG. 1 illustrates a flowchart of a method in accordance with a firstembodiment. The method for manufacturing a circuit board 100 a (shown inFIG. 8 ) is provided by way of embodiments, as there are a variety ofways to carry out the method. Each block shown in FIG. 1 represents oneor more processes, methods, or subroutines carried out in the method.Furthermore, the illustrated order of blocks is by example only and theorder of the blocks can be changed. Additional blocks may be added orfewer blocks may be utilized, without departing from this disclosure.The method can begin at block 201.

At block 201, referring to FIG. 2 , a single-sided board 10 is provided.The single-sided board 10 comprises a first insulating base 11 and acopper layer 13 covering a surface of the first insulating base 11. Atleast one first through hole 101 is defined in the single-sided board10. Each of the at least one first through hole 101 passes through thefirst insulating base 11 to expose the copper layer 13. The single-sidedboard 10 further comprises at least one first conductive structure 15each fully infilled in the at least one first through hole 101.

Each of the at least one first conductive structure 15 may protrude froma surface of the first insulating base 11 facing away from the copperlayer 13.

At block 202, referring to FIG. 3 , a laminated board 20 is provided.The laminated board 20 comprises a metal layer 24, a third insulatingbase 23, a metal shielding layer 22, and a second insulating base 21arranged in that sequence.

At block 203, referring to FIG. 4 , a wiring layer 240 is formed by themetal layer 24 of the laminated board 20, and comprises at least onesignal wire 241 and at least one connecting pad 242.

In at least one embodiment, the wiring layer 240 comprises a signal wire241 and two connecting pads 242. The signal wire 241 is between the twoconnecting pads 242.

At block 204, referring to FIG. 5 , at least one second through hole 201is defined in the laminated board 20. Each of the at least one secondthrough hole 201 passes through the second insulating base 21, the metalshielding layer 22, and the third insulating base 23 to expose one ofthe at least one connecting pad 242.

In at least one embodiment, the at least one second through hole 201 isdefined by laser. In another embodiment, the at least one second throughhole 201 may be defined by mechanical cutting or etching.

In another embodiment, each of the at least one second through hole 201further passes through a portion of the corresponding connecting pad242, thereby forming a hollow (not shown) in the correspondingconnecting pad 242.

At block 205, referring to FIG. 6 , a second conductive structure 25 isfully infilled in each of the at least one second through hole 201,thereby obtaining a middle structure 200.

In at least one embodiment, an end portion of the second conductivestructure 25 connect the corresponding at least one connecting pad 242,and another end portion of the second conductive structure 25 protrudesfrom a surface of the second insulating base 21 facing away from themetal shielding layer 22.

In at least one embodiment, the second conductive structure 25 is formedby conductive paste filling each of the at least one second through hole201. In another embodiment, the second conductive structure 25 may bemade of other material, such as metal, and may be formed by othermethod, such as electroplating.

In another embodiment, the end portion of the second conductivestructure 25 connecting the corresponding at least one connecting pad242 can be embedded into the corresponding at least one connecting pad242.

At block 206, referring to FIG. 7 , a double-sided board 30 is provided.The double-sided board 30 comprises a wiring layer 330, a fourthinsulating base 32, and a first copper foil 31 arranged in thatsequence. The wiring layer 330 comprises at least one signal wire 331and at least one connecting pad 332. The double-sided board 30 furthercomprises at least one third conductive structure 35 each passingthrough the fourth insulating base 32 and connecting one of the at leastone connecting pad 332 and the first copper foil 31.

In at least one embodiment, the wire layer 330 comprises a signal wire331 and two connecting pads 332. The signal wire 331 is between the twoconnecting pads 332.

At block 207, referring to FIG. 8 , the single-sided board 10, at leastone middle structure 200, and the double-sided board 30 are pressed inthat sequence to form the circuit board 100 a. Each of the at least onefirst conductive structure 15 connects one of the at least oneconnecting pad 242 of the middle structure 200 adjacent to thesingle-sided board 10. Each of the at least one connecting pad 332connects one of the at least one second conductive structure 25 of themiddle structure 200 adjacent to the double-sided board 30. When thenumber of the at least one middle structure 200 is greater than one,each of the at least one second conductive structure 25 of one of the atleast one middle structures 200 connects to another corresponding secondconductive structure 25 through a corresponding at least one connectingpad 242 of a next one of the at least one middle structure 200.

In at least one embodiment, the number of the at least one middlestructure 200 is two. In the circuit board 100 a, from top to bottom,comprises one single-sided board 10, a first middle structure 200, asecond middle structure 200, and the double-sided board 30. An endportion of each at least one first conductive structure 15 facing awayfrom the copper layer 13 connects an end portion of a at least oneconnecting pad 242 of the first middle structure 200 facing away fromthe metal shielding layer 22 of the first middle structure 200. An endportion of each second conductive structure 25 of the first middlestructure 200 facing away from the connecting pad 242 of the firstmiddle structure 200 connects an end portion of a corresponding at leastone connecting pad 242 of the second middle structure 200 facing awayfrom the metal shielding layer 22 of the second middle structure 200. Anend portion of each second conductive structure 25 of the second middlestructure 200 facing away from the at least one connecting pad 242 ofthe second middle structure 200 connects an end portion of acorresponding at least one connecting pad 332 facing away from the firstcopper foil 31. The first insulating base 11 is combined with the thirdinsulating base 23 of the first middle structure 200 to form adielectric layer to wrap the wiring layer 240 of the first middlestructure 200. The second insulating base 21 of the first middlestructure 200 is combined with the third insulating base 23 of thesecond middle structure 200 to form a dielectric layer to wrap thewiring layer 240 of the second middle structure 200. The secondinsulating base 21 of the second middle structure 200 is combined withthe fourth insulating base 32 to form a dielectric layer to wrap thewiring layer 330.

Each of the wiring layer is sandwiched between the copper layer 13 andone shielding layer 22, or between one first copper foil 31 and oneshielding layer 22, or between two shielding layers 22. As a result,each of the wiring layer can be protected from electromagneticinterference.

FIG. 9 illustrates a flowchart of an embodiment of a method formanufacturing the single-sided board 10. The method can begin at block501.

At block 501, referring to FIG. 10 , a single-sided copper clad laminate10 a is provided. The single-sided copper clad laminate 10 a comprises afirst insulating base 11 and a copper layer 13 covering a surface of thefirst insulating base 11.

In at least one embodiment, the first insulating base 11 may be adielectric material having a dielectric constant less than 3.4 and adielectric dissipation factor less than 0.005, such as liquidcrystalline polymer, polyetheretherketone, or modified polyimide. Inanother embodiment, the first insulating base 11 can be other dielectricmaterial as needed.

At block 502, referring to FIG. 11 , an insulating removable layer 16 ispressed on a surface of the first insulating base 11 facing away fromthe copper layer 13. At least one hole 103 each passing through theinsulating removable layer 16 and the first insulating base 11 isdefined to expose the copper layer 13. Each of the at least one hole 103comprises a first through hole 101 passing through the first insulatingbase 11.

At block 503, referring to FIG. 2 , a first conductive structure 15 isformed in each of the at least one hole 103 to be fully infilled in theat least one hole 103, and the insulating removable layer 16 is removed,thereby obtaining the single-sided board 10. An end portion of the atleast one first conductive structure 15 connects the copper layer 13,another end portion of the at least one first conductive structure 15protrudes from a surface of the first insulating base 11 facing awayfrom the copper layer 13.

In at least one embodiment, the at least one first conductive structure15 is formed by conductive paste filling each of the at least one hole103. In another embodiment, the at least one first conductive structure15 may be formed by electroplating.

FIG. 12 illustrates a flowchart of an embodiment of a method formanufacturing the laminated board 20. The method can begin at block 601.

At block 601, referring to FIG. 13 , a second insulating base 21 isprovided, and a metal shielding layer 22 is formed on a surface of thesecond insulating base 21.

In at least one embodiment, the surface of the second insulating base 21is roughened, a seed layer 221 is formed on the roughened surface, and ametal thickening layer 222 is formed on a surface of the seed layer 221facing away from the second insulating base 21. The metal shieldinglayer 22 is formed by the seed layer 221 and the metal thickening layer222.

The seed layer 221 can be made by coating, electroplating, electrolessplating, ion plating, or sputter coating. In at least one embodiment,the seed layer 221 is made by coating a composition on the roughenedsurface. The composition comprises an initiator, a monomeric compound,CuBr₂, sparteine, and silver powders. The initiator has a masspercentage of about 0.036% to about 1.36% of a total mass of thecomposition. The monomeric compound has a mass percentage of about 10%to about 20% of a total mass of the composition. CuBr₂ has a masspercentage of about 0.028% to about 0.28% of a total mass of thecomposition. Sparteine has a mass percentage of about 0.09% to about0.9% of a total mass of the composition. Silver powders have a masspercentage of about 80% to about 90% of a total mass of the composition.

In at least one embodiment, the seed layer 221 has a thickness of about0.1 μm to about 1 μm.

The metal thickening layer 222 may be made by electroplating orelectroless plating.

At block 602, referring to FIG. 14 , a third insulating base 23 isformed on a surface of the metal shielding layer 22 facing away from thesecond insulating base 21.

The third insulating base 23 can be made by coating an insulatingmaterial on the metal shielding layer 22, and curing the insulatingmaterial. In another embodiment, the third insulating base 23 may bepressed on the metal shielding layer 22 directly.

In at least one embodiment, each of the second insulating base 21 andthe third insulating base 23 may be a dielectric material having adielectric constant less than 3.4 and a dielectric dissipation factorless than 0.005, such liquid crystalline polymer, polyetheretherketone,or modified polyimide.

At block 603, referring to FIG. 3 , a metal layer 24 is formed on asurface of the third insulating base 23 facing away from the metalshielding layer 22, thereby obtaining the laminated board 20.

The metal layer 24 may be formed by metallization, or pressing a metalfoil on the third insulating base 23.

FIG. 15 illustrates a flowchart of an embodiment of a method formanufacturing the double-sided board 30. The method can begin at block701.

At block 701, referring to FIG. 16 , a double-sided copper clad laminate30 a is provided. The double-sided copper clad laminate 30 a comprises afirst copper foil 31, a fourth insulating base 32, and a second copperfoil 33 arranged in that sequence.

At block 702, referring to FIG. 17 , a wiring layer 330 is formed by thesecond copper foil 33, and comprises at least one signal wire 331 and atleast one connecting pad 332.

At block 703, referring to FIG. 7 , at least one third through hole 301passing through the fourth insulating base 32 is defined. The firstcopper foil 31 communicates with one of the at least one connecting pad332 via the at least one third through hole 301. A third conductivestructure 35 formed in each of the at least one third through hole 301to connect the first copper foil 31 to one of the at least oneconnecting pad 332.

In at least one embodiment, each of the at least one third through hole301 passes through the first copper foil 31 and the fourth insulatingbase 32 to expose one of the at least one connecting pad 332.

In another embodiment, each of the at least one third through hole 301further passes through a portion of or an entire correspondingconnecting pad 332, and the third conductive structure 35 is embeddedinto the corresponding connecting pad 332.

In another embodiment, referring to FIGS. 18 and 6 , an insulatingremovable layer 26 is pressed on a surface of the second insulating base21 facing away from the metal shielding layer 22, and then the at leastone second through hole 201 passing through the insulating removablelayer 26, the second insulating base 21, the metal shielding layer 22,and the third insulating base 23 is defined to expose a corresponding atleast one connecting pad 242. The insulating removable layer 26 isremoved after forming the second conductive structure 25, to cause thesecond conductive structure 25 to protrude from a surface of the secondinsulating base 21 facing away from the metal shielding layer 22, asshown in FIG. 6 .

FIG. 19 illustrates a flowchart of a second embodiment of a method formanufacturing the circuit board 100 b. The method can begin at block801.

At block 801, two single-sided boards 10 as shown in FIG. 2 is provided.

At block 802, referring to FIG. 20 , a laminated structure 40 isprovided. The laminated structure 40 comprises a metal layer 44, a thirdinsulating base 43, a metal shielding layer 42, a second insulating base41, and another metal layer 45.

In at least one embodiment, compared with the method of manufacturingthe laminated board 20, a method of manufacturing the laminatedstructure 40 further comprises forming another metal layer 45 on asurface of the second insulating layer 41 facing away from the metalshielding layer 42.

The metal layer 45 may be formed by metallization, or pressing a metalfoil on the second insulating base 41.

At block 803, referring to FIG. 21 , a wiring layer 440 and a wiringlayer 450 are formed by the metal layers 44 and 45 respectively. Eachwiring layer 440, 450 comprises at least one signal wire 441, 451respectively, and at least one connecting pad 442, 452, respectively.

At block 804, referring to FIG. 22 , at least one connecting hole 401 isdefined. Each of the at least one connecting hole 401 passes through oneconnecting pad 452, the second insulating base 41, the metal shieldinglayer 42, and the third insulating base 43. Each of the at least oneconnecting pad 442 is communicated with a corresponding at least oneconnecting pad 452 through the connecting hole 401.

In at least one embodiment, each of the at least one connecting hole 401just passes through one connecting pad 452, the second insulating base41, the metal shielding layer 42, and the third insulating base 43.

At block 805, referring to FIG. 23 , an electrical connecting structure46 is fully infilled in each of the at least one connecting hole 401,thereby obtaining a middle body 400. Each of the electrical connectingstructure 46 connects the one of the at least one connecting pad 442 toa corresponding connecting pad 452.

The electrical connecting structure 46 is formed by conductive pastefilling in each of the at least one connecting hole 401. In anotherembodiment, the electrical connecting structure 46 may be made of othermaterial, such as metal, and may be formed by other method, such aselectroplating.

At block 806, referring to FIG. 24 , the middle body 400 is sandwichedbetween two single-sided boards 10, and is pressed with two single-sidedboards 10 to form the circuit board 100 b. Each of the at least oneconnecting pad 442 and the at least one connecting pad 452 connects anend portion of one of the at least one first conductive structure 15 oftwo single-sided boards 10 facing away from the corresponding copperlayer 13.

In at least one embodiment, at least one middle structure 200 may bebetween two single-sided boards 10 when pressing to form the circuitboard 100 b.

In the illustrated embodiment in FIG. 24 , the number of the at leastone middle structure 200 is two and the middle structures 200 arelocated in a same side of the middle body 400. In the circuit board 100b, from bottom to top, comprises a first single-sided board 10, a middlebody 400, a first middle structure 200, a second middle structure 200,and a second single-sided board 10. The embodiment as shown in FIG. 24differs from the first embodiment described above, an end portion ofeach second conductive structure 25 of the second middle structure 200facing away from the at least one connecting pad 242 of the secondmiddle structure 200 connects an end portion of one of the at least oneconnecting pad 442 facing away from the metal shielding layer 42. An endportion of each of the at least one connecting pad 452 facing away fromthe metal shielding layer 42 connects an end portion of one of the atleast one first conductive structure 15 of the first single-sided board10 facing away from the copper layer 13 of the first single-sided board10.

In another embodiment, referring to FIG. 25 , the first middle structure200 and the second middle structure 200 are located on the opposite sideof the middle body 400 respectively. In a circuit board 100 c, from topto bottom, comprises a first single-sided board 10, a first middlestructure 200, a middle body 400, a second middle structure 200, and asecond single-sided board 10. The embodiment as described in FIG. 25differs from the first embodiment as described above, an end portion ofeach second conductive structure 25 of the first middle structure 200facing away from the connecting pad 242 of the first middle structure200 connects an end portion of one of the at least one connecting pad442 facing away from the metal shielding layer 42. An end portion ofeach of the at least one connecting pad 452 facing away from the metalshielding layer 42 connects an end portion of each second conductivestructure 25 of the second middle structure 200 facing away from the atleast one connecting pad 242 of the second middle structure 200. An endportion of each of the at least one connecting pad 242 of the secondmiddle structure 200 facing away from the metal shielding layer 22 ofthe second middle structure 200 connects an end portion of one of the atleast one first conductive structure 15 of the second single-sided board10 facing away from the copper layer 13 of the second single-sided board10.

In another embodiment, the at least one connecting hole 401 may bepassing through a portion of or an entire at least one connecting pad442. The electrical connecting structure 46 is embedded in the at leastone connecting pad 442.

The laminated board 20 comprises the metal layer 24 and the metalshielding layer 22, the laminated structure 40 comprises the metal layer44, the metal shielding layer 42, and another metal layer 45. Then thewiring layer is formed by the metal layer, and the wiring layerelectrically connects the metal shielding layer. That is, in the methodfor manufacturing the circuit board, the wiring layer is electricallyconnected to the metal shielding layer before pressing. As a result, themethod can reduce an alignment tolerance when pressing.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. It is also to be understood that the description and the claimsdrawn to a method may include some indication in reference to certainsteps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

FIG. 26 illustrates an embodiment of a circuit board 100 d. The circuitboard 100 d comprises N+1 number of the metal shielding layers 53, Nnumber of the wiring layer(s) 54, and N number of the dielectriclayer(s) 55, wherein N is a natural number. Each of the dielectric layer55 is sandwiched between every two adjacent metal shielding layers 53,and surrounds one of the wiring layer 54. Each of the wiring layer 54comprises at least one signal wire 541 and at least one connecting pad543. Each of the at least one connecting pad 543 connects the adjacentmetal shielding layers 53 by the conductive structure 56 embedded in thedielectric layer 55. Each of the metal shielding layers 53 surrounded bythe dielectric layer 55 comprises the seed layer 531 and the metalthickening layer 532 formed on the seed layer 531.

The seed layer 531 has a thickness of about 0.1 μm to about 1 μm.

It is to be understood, even though information and advantages of thepresent embodiments have been set forth in the foregoing description,together with details of the structures and functions of the presentembodiments, the disclosure is illustrative only; changes may be made indetail, especially in matters of shape, size, and arrangement of partswithin the principles of the present embodiments to the full extentindicated by the plain meaning of the terms in which the appended claimsare expressed.

What is claimed is:
 1. A method for manufacturing a circuit board,comprising: providing a single-sided board comprising a first insulatingbase, a copper layer covering a surface of the first insulating base, atleast one first through hole each passing through the first insulatingbase to expose the copper layer, and at least one first conductivestructure each infilled in one of the at least one first through hole;forming at least one middle structure, each of the middle structurebeing formed by: providing a laminated board comprising a metal layer, athird insulating base, a metal shielding layer, and a second insulatingbase arranged in that sequence; forming a wiring layer by the metallayer, the wiring layer comprising at least one signal wire and at leastone connecting pad; defining at least one second through hole eachpassing through the second insulating base, the metal shielding layer,and the third insulating base to expose one of the at least oneconnecting pad; and forming a second conductive structure infilled ineach of the at least one second through hole; providing a double-sidedboard comprising a wiring layer, a fourth insulating base, and a firstcopper foil arranged in that sequence, the wiring layer of thedouble-sided board comprising at least one signal wire and at least oneconnecting pad, the double-sided board further comprising at least onethird conductive structure each connecting one of the at least oneconnecting pad and the first copper foil; and pressing the single-sidedboard, the at least one middle structure, and the double-sided board inthat sequence to form the circuit board; wherein each of the at leastone first conductive structure connects one of the at least oneconnecting pad of an adjacent one of the middle structure, each of theat least one connecting pad of the double-sided board connects onesecond conductive structure of the adjacent middle structure; when thecircuit board comprises at least two middle structures, the two adjacentmiddle structures connect with each other by connecting the secondconductive structure of one of the middle structures with thecorresponding connecting pad of the adjacent middle structure.
 2. Themethod of claim 1, wherein each of the wiring layer in the laminatedboard and in the double-sided board comprises at least one signal wireand at least two connecting pads, the at least one signal wire beinglocated between the at least two connecting pads of each wiring layer.3. The method of claim 1, wherein providing the laminated board furthercomprising: providing the second insulating base, and roughening asurface of the second insulating base; forming a seed layer on theroughened surface; forming a metal thickening layer on a surface of theseed layer facing away from the second insulating base, the seed layerand the metal thickening layer forming the metal shielding layer;forming the third insulating base on a surface of the metal shieldinglayer facing away from the second insulating base; and forming a metallayer on a surface of the third insulating base facing away from themetal shielding layer, thereby obtaining the laminated board.
 4. Themethod of claim 1, wherein forming the at least one middle structurefurther comprising: before defining the second through hole, pressing aninsulating removable layer on a surface of the second insulating basefacing away from the metal shielding layer; defining the second throughhole further passing through the insulating removable layer on thesecond insulating base; and after forming the second conductivestructure, removing the insulating removable layer on the secondinsulating base wherein the second conductive structure protrudes from asurface of the second insulating base facing away from the metalshielding layer.
 5. A method for manufacturing a circuit board,comprising: providing a single-sided board comprising a first insulatingbase, a copper layer covering a surface of the first insulating base, atleast one first through hole each passing through the first insulatingbase to expose the copper layer, and at least one first conductivestructure each infilled in one of the at least one first through hole;forming a middle body by: providing a laminated structure comprising ametal layer, a third insulating base, a metal shielding layer, a secondinsulating base, and another metal layer arranged in that sequence;forming a wiring layer by each metal layer, each wiring layer comprisingat least one signal wire and at least one connecting pad; defining atleast one connecting hole each passing through the connecting pad of thelaminated structure, the second insulating base, the metal shieldinglayer, and the third insulating base, to communicate two connecting padsof two wiring layers of the laminated structure with each other; andforming an electrical connecting structure infilled in each of the atleast one connecting hole; pressing the single-sided board, the middlebody, and another the single-sided board in that sequence to form thecircuit board; wherein the connecting pads of two wiring layers of themiddle body connect the at least one first conductive structure of onesingle-sided board respectively.
 6. The method of claim 5, whereinproviding the laminated structure further comprises: providing thesecond insulating base, and roughening a surface of the secondinsulating base; forming a seed layer on the roughened surface; forminga metal thickening layer on a surface of the seed layer facing away fromthe second insulating base, wherein the seed layer and the metalthickening layer form the metal shielding layer; forming the thirdinsulating base on a surface of the metal shielding layer facing awayfrom the second insulating base; and forming a metal layer on a surfaceof the third insulating base facing away from the metal shielding layer,and forming another metal layer on a surface of the second insulatingbase facing away from the metal shielding layer, thereby obtaining thelaminated structure.